Flu Vaccine Safety and Pregnancy

Why should pregnant women get a flu shot?

Flu is more likely to cause severe illness in pregnant women than in healthy women who are not pregnant. Changes in the immune system, heart, and lungs during pregnancy make pregnant women (and women who have given birth during the past 2 weeks) more prone to severe illness from flu, including illness resulting in hospitalization. In addition, studies have shown that vaccinating a pregnant woman also can protect a baby after birth from flu. (Mom passes antibodies on to her developing baby that will protect against flu for the first several months after birth.)

CDC recommends that pregnant women get a flu shot during any trimester of their pregnancy to protect themselves and their newborn babies from flu. There is a lot of evidence that flu vaccines can be given safely during pregnancy, though these data are limited for the first trimester. The nasal spray vaccine is not recommended for use in pregnant women. To learn more about flu and pregnant women, please visit Pregnant Women & Influenza (Flu).

Is it safe for pregnant women and their developing babies to get a flu shot?

Yes. Flu shots have been given to millions of pregnant women over many years with a good safety record. There is a large body of scientific studies that supports the safety of flu vaccine in pregnant women and their babies. CDC continues to gather data on this topic.

Can flu vaccination result in miscarriage?

Multiple studies have shown that women who have gotten flu shots during pregnancy have not had a higher risk for spontaneous abortion (miscarriage); however, a recent study showed that women in early pregnancy who received two consecutive annual flu shots during 2010-11 and 2011-12, did have an increased risk of miscarriage in the 28 days after receiving the second vaccine. There is an ongoing investigation to study this issue further. CDC will analyze and consider additional findings as soon as they become available. At this time, however, the Advisory Committee on Immunization Practices (ACIP), the American College of Obstetricians and Gynecologists (ACOG) and CDC continue to recommend that pregnant women get a flu vaccine during any trimester of their pregnancy because flu poses a danger to pregnant women and a flu vaccine can prevent serious illness, including hospitalization, in pregnant women. A fact sheet with more information on this topic is available. Any pregnant woman who has questions about vaccines should talk to her doctor.

What side effects have pregnant women experienced from flu shots?

The most common side effects experienced by pregnant women are the same as those experienced by other people. They are generally mild and include:

• Soreness, redness, and/or swelling from the shot
• Fainting
• Headache
• Fever
• Muscle aches
• Nausea
• Fatigue

If side effects occur, they usually begin soon after the shot is given and generally last for 1-2 days.

Rarely, flu shots can cause serious problems like severe allergic reactions. Anyone with a severe, life-threatening allergy to any of the vaccine ingredients should not get the shot.

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Can pregnant women with egg allergies get vaccinated?

Most people who have an allergy to eggs can get vaccinated, with some additional safety measures. A person with severe (life-threatening) allergy to any vaccine component, including egg protein, should not get the shot, even if she is pregnant. Pregnant women should tell the person giving the shots if they have any severe allergies or if they have ever had a severe allergic reaction following a flu shot.

How is the safety of flu vaccines in pregnant women monitored?

CDC and FDA conduct ongoing safety monitoring of vaccines licensed for use in the United States.

CDC and FDA monitor flu vaccine safety during pregnancy during each influenza season using the Vaccine Adverse Event Reporting System (VAERS): An early warning system that helps CDC and FDA monitor health concerns following vaccination.  Anyone can report possible vaccine side effects to VAERS. Generally, VAERS reports cannot determine if a health concern that arises after vaccination (adverse event) was caused by a vaccine, but these reports can help indicate if further investigations are needed.

In addition CDC conducts research studies in the Vaccine Safety Datalink (VSD): A collaboration between CDC and nine health care organizations which allows ongoing monitoring and proactive searches of vaccine-related data.

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What studies has CDC conducted on flu vaccine safety during pregnancy?

Several studies conducted by CDC and partners support the safety of the flu vaccine for pregnant women and their babies.

1. Review of reports to the Vaccine Adverse Reporting System (VAERS) (Moro et al, 2011, Moro et al, 2011, Moro et al, 2017) found no evidence to suggest a link between pregnancy complications or adverse fetal outcomes among pregnant women and flu shots.
2. A study using VSD data (Irving et al, 2013) found no increased risk of miscarriage among pregnant women who received flu vaccines in the 2005-06 or 2006-07 flu seasons.
3. A large study using VSD data (Kharbanda et al, 2013) found no increased risk for adverse obstetric events (like chorioamnionitis, pre-eclampsia, or gestational hypertension) for pregnant women who received the flu vaccine from 2002 to 2009 when compared to pregnant woman who were not vaccinated.
4. A VSD study (Nordin et al, 2014) compared pregnant women who received the flu shot with an equal number of pregnant women who did not receive the flu shot during the 2004-05 and 2008-09 flu seasons. The study found no differences between the two groups in the rates of premature delivery or small for gestational age infants.
5. A large August 2017 study using VSD datafound that the babies of women who received the flu shot during their first trimester had no increased risk of having children with major birth defects.

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Where should a pregnant woman get vaccinated?

There are many different options for pregnant women to receive the flu shot, including a health care provider’s office, at work, a store, or a supermarket. All these places give flu vaccines that are licensed and approved for use in the United States. If you’ve never had a problem when previously receiving a flu vaccine, then there is no reason you can’t get a flu vaccine at work, a store, or a supermarket.

What about thimerosal in flu vaccines? Should pregnant women get thimerosal-free flu vaccines?

Studies have shown the small amount of thimerosal in vaccines does not cause harm. There is thimerosal-free flu vaccine available for people who want to avoid thimerosal. More information about thimerosal can be found at Thimerosal and Flu Vaccines”

Can a breastfeeding woman get a flu vaccine?

Yes. Breastfeeding women should get the flu vaccine to protect themselves from flu. Getting vaccinated reduces mothers’ risk of getting sick and of passing the flu on to their babies, thus protecting their babies from flu also. This is especially important for children younger than 6 months old since they are too young to receive influenza vaccine themselves.

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